Macrophage ATP citrate lyase deficiency stabilizes atherosclerotic plaques

Abstract

Macrophages represent a major immune cell population in atherosclerotic plaques and play central role in the progression of this lipid-driven chronic inflammatory disease. Targeting immunometabolism is proposed as a strategy to revert aberrant macrophage activation to improve disease outcome. Here, we show ATP citrate lyase (Acly) to be activated in inflammatory macrophages and human atherosclerotic plaques. We demonstrate that myeloid Acly deficiency induces a stable plaque phenotype characterized by increased collagen deposition and fibrous cap thickness, along with a smaller necrotic core. In-depth functional, lipidomic, and transcriptional characterization indicate deregulated fatty acid and cholesterol biosynthesis and reduced liver X receptor activation within the macrophages in vitro. This results in macrophages that are more prone to undergo apoptosis, whilst maintaining their capacity to phagocytose apoptotic cells. Together, our results indicate that targeting macrophage metabolism improves atherosclerosis outcome and we reveal Acly as a promising therapeutic target to stabilize atherosclerotic plaques.

Myeloid ATP Citrate Lyase Regulates Macrophage Inflammatory Responses In Vitro Without Altering Inflammatory Disease Outcomes

“…Among them, the 5 genes that were significantly altered in naive Acly-deficient BMDMs compared to control BMDMs are mainly involved in lipid metabolism and cell cycle regulation, indicating that increased inflammatory responses are likely not due to differences at baseline (Supplementary Figure 1C). Il6 and Nos2 were among the most upregulated genes in LPS-stimulated Acly M-KO macrophages, corresponding with our earlier observations that Acly-deficient macrophages secrete more IL-6 and nitric oxide in response to LPS (12). Together, this analysis indicates that inflammatory signaling is increased in LPS-activated Acly M-KO macrophages in vitro.…”

“…Likewise, systemic inhibition of Acly in vivo reduces inflammatory outcomes in endotoxin-induced peritonitis (7). However, through a recently developed myeloid-specific Acly knockout mouse model, we revealed a discrepancy in the translation of in vitro findings to in vivo settings (12). In contradiction to previous studies, LysM-Cre-mediated Acly-deficient macrophages revealed increased inflammatory signaling in in vitro LPS-elicited responses and in atherosclerotic plaques in vivo (12).…”

“…In contradiction to previous studies, LysM-Cre-mediated Acly-deficient macrophages revealed increased inflammatory signaling in in vitro LPS-elicited responses and in atherosclerotic plaques in vivo (12). Despite increased inflammatory signaling, myeloid Acly deficiency resulted in increased atherosclerotic plaque stability (12). These data underline the need for a better understanding of targeting of Acly in macrophages specifically in the potential treatment of acute and chronic immune disorders.…”

“…However, through a recently developed myeloid-specific Acly knockout mouse model, we revealed a discrepancy in the translation of in vitro findings to in vivo settings (12). In contradiction to previous studies, LysM-Cre-mediated Acly-deficient macrophages revealed increased inflammatory signaling in in vitro LPS-elicited responses and in atherosclerotic plaques in vivo (12). Despite increased inflammatory signaling, myeloid Acly deficiency resulted in increased atherosclerotic plaque stability (12).…”

“…To study the effects of Acly deficiency on inflammatory responses in macrophages, we crossed Acly fl/fl mice with mice expressing Cre under control of the myeloid cell-specific LysM promotor (Lyz2-Cre) (12). We have previously shown that naïve, unstimulated Acly-deficient bone marrow-derived macrophages (BMDMs) display deregulated lipid metabolism compared to control BMDMs, whereas inflammatory cytokines were increased only after LPS stimulation (12). Hence, we stimulated control (Acly fl/fl ) and Acly-deficient (Acly M-KO ) bone marrow-derived macrophages (BMDMs) in vitro with LPS for 3 and 24 hours to examine inflammatory activation in an unbiased way through RNA-seq (Figure 1A).…”